The present invention generally relates to a method and apparatus for testing electronic trip units. More specifically, the present invention relates to a tester for suitably testing the connection between a trip unit and an actuator within a circuit breaker, and a method and circuit breaker usable with the tester.
A circuit breaker typically includes a pair of electrical contacts that, when closed, allows circuit current to pass to a protected portion of an electrical distribution circuit via the closed contacts. When the contacts open, circuit current is prevented from flowing from one contact member to the other, and therefore, circuit current is prevented from flowing to the protected portion of the distribution circuit. The use of electronic trip units (trip units) in such circuit breakers is well known.
An electronic trip unit typically comprises voltage and current sensors, which provide analog signals indicative of the current flowing through the circuit breaker to a protected portion of an electrical distribution circuit. The analog signals are converted by an A/D (analog/digital) converter to digital signals, which are processed by a microcontroller. The trip unit further includes RAM (random access memory), ROM (read only memory) and EEPROM (electronic erasable programmable read only memory) all of which interface with the microcontroller. The ROM includes trip unit application code, e.g., main functionality firmware, including initializing parameters, and boot code. The EEPROM includes operational parameters for the application code.
In response to an overcurrent condition in the electrical distribution circuit, the electronic trip unit generates a trip signal, which is provided to an actuator within the circuit breaker. In response to the trip signal, the actuator, which includes a solenoid or similar electromechanical device, mechanically actuates (trips) an operating mechanism within the circuit breaker. The operating mechanism separates the electrical contacts to stop the flow of electrical current to the protected circuit.
The electronic trip unit and the actuator are typically separate components mounted within the circuit breaker""s housing. Thus, when a circuit breaker is assembled, an electrical connection must be established between the electronic trip unit and the actuator. This connection is made within the circuit breaker housing and is, therefore, not visible when the circuit breaker housing is fully assembled. Operability of the circuit breaker depends upon the electrical connection between the trip unit and the actuator. Therefore, this connection must be checked during initial circuit breaker construction and periodically through the life of the circuit breaker. Unfortunately, a visual check can be made only by partially disassembling the circuit breaker, which increases construction and maintenance costs.
The above discussed and other drawbacks and deficiencies are overcome or alleviated by a circuit breaker having a housing, a trip unit within the housing, an actuator electrically connected to said trip unit, a first terminal and a second terminal, the circuit breaker adapted to connect to an electrical distribution circuit through the first terminal and the second terminal, a test jack provided on the housing, a jack terminal separate from the first terminal and the second terminal provided within the test jack, the jack terminal electrically connected to an electrical connection between the actuator and the trip unit, wherein the electrical connection between the actuator and the trip unit can be tested without disassembling the circuit breaker.
A method for testing an electrical connection between a trip unit and an actuator within a circuit breaker is also disclosed, where the circuit breaker includes a first terminal and a second terminal for connecting the circuit breaker to an electrical distribution circuit, and a test jack housing a jack terminal, the jack terminal separate from the first and second terminals, the jack terminal electrically connected to the trip unit. The method includes plugging a plug of a tester within the test jack of the circuit breaker, the tester also having a casing, the plug extending from the casing, a power source, an energy storage element electrically connected to the power source, and a two loop switch electrically connected to the power source and the energy storage element. The method also includes charging the energy storage element within the tester by positioning the two loop switch in a charge position, and releasing energy from the energy storage element in the tester to the actuator in the circuit breaker through the electrical connection, wherein releasing energy from the energy storage element in the tester includes positioning the two loop switch in a discharge position.